Acute respiratory distress syndrome (ARDS) is the most extreme form of acute lung injury (ALI) that results in a loss of lung function and structure. Vascular endothelial growth factor (VEGF), a protein critical for lung development that is found in the thin layer of liquid lining the inner surface of the lung air sacs, is believed to play a key role in the development of ARDS. During ARDS/ALI, VEGF markedly increases the permeability of the cells lining the inner surface of blood vessels in the lungs, which leads to an accumulation of fluid in the lungs (pulmonary edema), a characteristic of ARDS/ALI. Thus, anti-VEGF therapies offer a unique approach to treat this potentially fatal disorder. Bevacizumab (Avastin ®), an anti-VEGF medication, has been shown to be effective in inhibiting pulmonary edema caused by VEGF over-expression in an animal model.